Control valve for hydraulic actuator



y 2, 1962 R. E. PRUNTY 3,035,610

CONTROL VALVE FOR HYDRAULIC ACTUATOR Filed Sept. 10, 1959 2 Sheets-Sheet 1 IN V EN TOR.

May 22, 1962 R. E. PRUNTY 3,

CONTROL VALVE FOR HYDRAULIC ACTUATOR Filed Sept. 10, 1959 2 Sheets-Sheet 2 E INVEN TOR.

United States Patent 3 035,610 CONTROL VALVE FOlR HYDRAULIC ACTUATOR Robert E. Prunty, Charles City, Iowa, assignor, by mesne assignments, to Oliver Corporation, Chicago, 111., a corporation of Delaware (1960 corporation) Filed Sept. 10, 1959, Ser. No. 839,122 4 Claims. (Cl. 137-621) This invention relates generally to control valves for hydraulic actuators, and particularly to a control valve for use in a hydraulic power system including a pump, a reservoir, and a hydraulic actuator having a single acting piston under load.

In the past, a close fit between the valve body and the lands on a spool of a control valve was relied upon to maintain a load in a raised position in the neutral position of the control valve. It has been found that such valves have short lives, especially under conditions conducive to contamination of the hydraulic fluid, and in addition, they are expensive to manufacture, involving close tolerances, super finishes, selective assembly, etc.

It is an object of the invention to provide an improved control valve.

Another object of the invention is to provide a control valve which has a longer life and is less costly to manufacture than former control valves.

A further object of the invention is to provide a control valve for a hydraulic actuator having a single acting piston under load, in which a separate lowering valve spool is provided which is isolated from return fiow from the actuator so as to be less subject to Wear.

A still further object of the invention is to provide a control valve for a hydraulic actuator having a single acting piston under load, in which maintaining of the load in position is not dependent upon the closeness of fit between a bore in the body of the control valve and a valve spool therein.

These and other objects will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein:

FIGURE 1 is a schematic sectional view of the control valve or" the invention, showing the neutral position thereof;

FIGURE 2 is a partial schematic view of the control valve in load raising position;

FIGURE 3 is a partial schematic view of the control valve in load lowering position; and

FEGURE 4 is a schematic diagram of the system, wherein V is the control valve, P is the pump, R is the reservoir, -A is the hydraulic actuator, and L is the load.

In FIGURE 1, a valve body is shown in section. A bore 12 therein is provided to receive a main control valve spool 14 operable from an end 16 thereof projecting from the body 10. Bores 18, 29, and 22 are also provided in valve body 10 to receive a lowering valve spool 24, a vent valve spool 26, and a flow control valve spool 28, respectively.

An inlet passage 30 opening to the outside of valve body 10 is provided therein and forms a pressure passage adapted to be connected in a suitable manner to the outlet of a pump (not shown) of the constant displacement type. Passage 30 intersects bores 12 and 22 as shown. A passage 32 opening to the outside of valve body 10 is provided therein and forms an outlet passage adapted to be connected to the reservoir (not shown) for the pump. The passage 32 intersects bore 22 as shown. The end of bore 12 opposite the end from which end 16 of main control valve spool 14 projects opens to the outside of valve body 10 and forms an outlet passage adapted to be connected to the reservoir.

A passage 34 opening to the outside of valve body 10 is provided therein and forms an inlet-outlet passage adapted to be connected to the cylinder of a single acting hydraulic actuator under load.

A passage 36 is provided in valve body 10 to connect bores 12 and 18. The passage 36 bypasses bore 20. A passage 38 is provided in valve body 10 adjacent passage 34 and has an open end thereof plugged by a threaded plug 40. A passage 42 is provided to connect passage 38 and bore 12, which are also connected by another smaller passage 44 which bypasses bore 20 and has a restrictive orifice 46 adjacent passage 38. The passage 32% is also connected to bore 20 by a passage 48 and to bore 22 by a passage 50 which bypasses bore 12. A passage 52 connects the inner end of bore 20 with passage 42.

A passage 54 intersects bore 12 adjacent the end leading to the reservoir and angles through valve body 10, bypassing passage 38 and intersecting a passage 56 having an open end plugged by a plug 58. A passage 60 is provided in valve body 10 to connect passage 56 with passages 34 and 38.

The plug 58 is recessed at its inner end to receive a compression spring 62 which urges a ball check valve 64 toward an annular seat 66 provided in passage 56. Similarly, the plug 40 is recessed at its inner end to receive a compression spring 68 which urges a ball check valve 70 toward an annular seat 72 provided in passage 33. The passage 42 is provided with an annular check valve seat 74 engageable by a ball check valve 76 urged toward seat 74 by a compression spring 78.

A bore is provided in valve body 10 between the inner end of bore 18 and passage 56 for mounting a plunger 80 by which ball check valve 64 may be operated. The

inner end of bore 18 is provided with a vent passage 82 forming an outlet passage adapted to be connected to the reservoir. The outer end of bore 18 is adapted to receive a retaining ring 84 for maintaining a plug 86 in bore 18. The plug 86 is centrally grooved to receive O-ring seal 88. A compression spring 90 is provided at the inner end of bore 18 for urging lowering valve spool 24 toward plug 36. The lowering valve spool 24 is hollow and open at the end thereof adjacent plug 86. Ports 92 at the open end of spool 24 connect the hollow interior thereof with bore 18 and passage 36.

The outer end of bore 20 also forms an outlet passage adapted to be connected to the reservoir, but is provided with an annular member 94 threaded into valve body 10 to provide a seat for a compression spring 96 which urges vent valve spool 26 inwardly. Vent valve spool 26 is hollow and open at its outer end. Lands 100 and 1112 thereon define an annular groove 104 which is connected to the hollow interior of spool 26 by ports 98.

The outer end of bore 22 is plugged by a plug 106 threaded into valve body 10 and providing a seat for a compression spring 108 which urges flow control valve spool 28 inwardly. A land 110 is provided on spool 28 to cooperate with the inner end of bore 22 between passages 30 and 32.

The main control valve spool 14 is provided with a plurality of lands and grooves, including lands 112, 114, 116, 113, 120, and 122. The spool 14 is hollow and open at the end thereof opposite end 16. Ports 124 adjacent land 112 and ports 126 between lands 118 and 121 connect the outside or" spool 14 with the hollow interior thereof.

The neutral position is shown in FIGURE 1. In this position, fluid from the pump directed to pressure passage 31) may flow around spool 14 in bore 12, through passage 44, orifice 46, passage 38, passage 48, and ports 93, and through the hollow interior of spool 26 and member 94 to the reservoir. In this flow path, orifice 46 presents the greatest resistance to flow, so that the pressure downstream thereof is substantially atmospheric. Therefore the pressure in passage 50, and in here 22 between flow control valve spool 28 and plug 106, is also very nearly atmospheric in this neutral position of the valve, and fluid in pressure passage 30 moves the valve spool 28 outwardly against the force of spring 108 to the position shown, allowing the greater portion of the fluid supplied to passage 30 by the pump to flow back to the reservoir through passage 32'. Flow from passage 30 to passage 42 is blocked by land 116, and flow from passage 30 to passage 36 is blocked by land 114 in the neutral position of the valve, passage 36 being slightly uncovered by land 112 and open to the reservoir through ports 124 and the hollow interior of spool 14, and passage 42 being sli htly uncovered by land 113 and open to the reservoir through ports 126 and the hollow interior of spool 14.

' In FIGURE 2, the valve is shown in load raising position, main control valve spool 14 having been shifted to the right from the neutral position. In this position, passage 42 is not blocked by land 116, so that fluid from the pump directed to pressure passage 30 may flow around spool 14 in bore 12, through passage 42 and check valve seat 74, through passage 38 and check valve seat 72, and out passage 34 to the cylinder of the hydraulic actuator. The pressure in passage 42 acts through passage 52 to move vent valve spool 26 to the left in bore to the position shown. In this position of spool 26, flow through passage 44, orifice 46, passage 38, and passage 48, to groove 104, ports 98, the interior of spool 26, and the reservoir, is blocked by land 100 on spool 26, so that passage 50 is no longer vented. Substantially full pump pressure then exists at both ends of flow control valve spool 28, and spring 108 acts to move spool 28 to the position shown, wherein passage 32 to the reservoir is blocked from passage by land 110, and full pump delivery goes to the cylinder of the hydraulic actuator. Flow from passage 30 to passage 36 is blocked by lands 112 and 114 of spool 14, and passages 36 and 54 are open to the reservoir through ports 124 and 126, respectively, and the interior of spool 14.

If the main control valve spool 14 is only moved part way from the position of FIGURE 1 to the position of FIGURE 2, the land 116 may be made to barely uncover passage 42, so that a considerable pressure drop may be made to occur across land 116. Less than full pump pressure will exist then in passages 42, 38, and 50, and at the right end of spool 28 in bore 22, and spool 28 will assume a position between the limits shown in FIGURE 1 and FIGURE 2, so' that part of the pump delivery will go to the cylinder of the hydraulic actuator to produce a throttled raise of the load, and the remainder of the pump delivery will be returned to the reservoir through passage 32. r

In FIGURE 3, the valve is shown in load lowering position, main control valve spool 14 having been shifted to the left from the neutral position of FIGURE 1. In this position, flow from passage 30 to passage 42 and the cylinder is blocked by lands 116 and 118, and passage 42 is open to the reservoir through ports 126 and the hollow interior of spool 14. With no pressure in the right end of bore 20, spool 26 will assume the position shown under the influence of spring 96, and passage 48' will be unblocked. Fluid may flow from pressure passage 30 through passage 44, orifice 46, passage 38, passage 48, groove 104, ports 98, and the hollow interior of spool 26 to the reservoir. The right end of bore 22 will also be open to the reservoir through passages 50, 38, 48, groove 104, ports 93, and the interior of spool 26. Pressure on the left end of spool 28 will then act against spring 108 and cause spool 28 to assume the position shown, in which the greater portion of the fluid supplied to passage 30 by the pump will flow back to the reservoir through passage 32. Flow from passage 36 through ports 124 and the interior of spool 14 to the reservoir is blocked by lands 112 and 114, and a portion of the fluid delivered to passage 30 by the pump will flow around spool 14 to passage 36 and into the interior of lowering valve spool 24 through ports 92 (FIGURE 1). The fluid pressure will move lowering valve spool 24 to the position shown in FIGURE 3 against the force of spring 90. The spool 24 will shift plunger to unseat ball check valve 64, and fluid from the cylinder of the hydraulic actuator will flow under pressure of the load through passages 34 and 60, check valve seat 66, passage 56, passage 54, and bore 12 to the reservoir.

If a throttled lowering of the load is desired, the spool 14 may be moved only part way from the position of FIGURE 1 to the position of FIGURE 3, so that land 122 barely uncovers passage 54 and the flow from passage 54 to bore 12 and the reservoir is throttled by land 122.

The main control valve spool 14 acts as a pilot valve with respect to vent valve spool 26 and lowering valve spool 24, but directly controls flow to the hydraulic actuator for the raising of the load. The provision of separate lowering valve spool 24 and ball check valve 64 operated thereby renders the maintaining of the load on the actuator in a given position entirely free of the closeness of fit between bore 12 and spool 14. Greatly increased valve life has resulted, along with lower manufacturing costs, greater interchangeability of parts, etc.

Variations and modifications may be made without departing from the spirit and scope of the invention.

The invention is claimed as follows:

1. A control valve for a hydraulic actuator comprising a valve body, a first bore in said valve body, a main control valve spool in said first bore, an inlet passage in said valve body communicating with said first bore and adapted to be connected to a pump, an outlet passage in said valve body adapted to be connected to a reservoir, an inlet-outlet passage in said valve body adapted to be connected to a hydraulic actuator, first passage means in said valve body connecting said first bore and said inlet-outlet passage, second passage means in said valve body separate from said first passage means and connecting said inlet-outlet passage and said outlet passage, a check valve in said second passage means connecting said inlet-outlet passage and said outlet passage normally preventing flow of fluid from said inletoutlet passage to said outlet passage, a second bore in said valve body, a lowering valve spool in said second bore, third passage means in said valve body separate from said first and second passage means and connecting said first and second bores, check valve operating means in said valve body operable by said lowering valve spool to open said check valve, means on said main control valve spool for controlling flow of fluid from said first bore through said first passage means to said inlet-outlet passage, reverse flow preventing means in said first pas sage means, means on said main control valve spool for controlling flow of fluid through said third passage means connecting said first and second bores for operating said lowering valve spool, and means providing a fluid bypass between said inlet passage and the reservoir when fluid is not flowing from said first bore to said inlet-outlet passage.

2. A control valve for a hydraulic actuator comprising a valve body, a first bore in said valve body having an end forming an outlet passage adapted to be connected to a reservoir, a main control valve spool in said first bore, an inlet passage in said valve body communicating with said first bore and adapted to be' connected to a pump, an inlet-outlet passage in said valve body adapted to be connected to a hydraulic actuator, first passage means in said valve body connecting said first bore and said inlet-outlet passage, second passage means in said valve body separate from said first passage means and connecting said inlet-outlet passage and said outlet passage, a check valve in said second passage means connecting said inlet-outlet passage and said outlet passage normally preventing flow of fluid from said inlet-outlet passage to said outlet passage, a second bore in said valve body, a lowering valve spool in said second bore, third passage means in said valve body separate from said first and second passage means and connecting said first and second bores, check valve operating means in said valve body operable by said lowering valve spool to open said check valve, means on said main control valve spool for controlling flow of fluid from said first bore through said first passage means to said inlet-outlet passage, check valve means in said first passage means preventing reverse fluid flow therethrough, means on said main control valve spool for controlling flow of fluid through said third passage means connecting said first aud second bores for operating said lowering valve spool, means on said main control valve spool for metering the flow of fluid from said inlet-outlet passage to said outlet passage, and means providing a fluid by-pass between said inlet passage and the reservoir when fluid is not flowing from said first bore to said inlet-outlet passage.

3. A control valve for a hydraulic actuator comprising a valve body, a first bore in said valve body having an end forming a first outlet passage adapted to be connected to a reservoir, a main control valve spool in said first bore, an inlet passage in said valve body communicating with said first bore and adapted to be connected to a pump, an inlet-outlet passage in said valve body adapted to be connected to a hydraulic actuator, passage means in said valve body connecting said first bore and said inlet-outlet passage, passage means in said valve body connecting said inlet-outlet passage and said first outlet passage, a check valve in said passage means connecting said inlet-outlet passage and said first outlet passage normally preventing flow of fluid from said inletoutlet passage to said first outlet passage, a second bore in said valve body, a lowering valve spool in said second bore, a passage in said valve body connecting said first and second bores, check valve operating means in said valve body operable by said lowering valve spool to open said check valve, means on said main control valve spool for controlling flow of fluid from said first bore to said inlet-outlet passage, means on said main control valve spool for controlling flow of fluid through said passage connecting said first and second bores for operating said lowering valve spool, means on said main control valve spool for metering the flow of fluid from said inlet-outlet passage to said first outlet passage, a third bore in said valve body communicating with said inlet passage, a second outlet passage in said valve body communicating with said third bore and adapted to be connected to said reservoir, a flow control valve spool in said third bore for controlling flow of fluid from said inlet passage to said second outlet passage, a passage in said valve body connecting said passage means from said first bore to said inlet-outlet passage and said third bore and communicating with said third bore adjacent the end of said flow control valve spool remote from said inlet passage, a fourth bore in said valve body communicating at one end with said passage means from said first bore to said inlet-outlet passage, a third outlet passage in said valve body communicating with the other end of said fourth bore, a passage in said valve body communicating at one end with said first bore and continuously open to said inlet passage around said main control valve spool and having a fixed orifice adjacent the other end in communication with said passage means from said first bore to said inlet-outlet passage, a passage in said valve body having one end communicating with said fixed orifice and communicating at its other end with said fourth bore between the ends thereof, and a vent valve spool in said fourth bore controlling flow of fluid from the passage communicating therewith between the ends thereof to said third outlet passage to thereby control venting and pressurizing of said third bore adjacent the end of said flow control valve spool remote from said inlet passage, said vent valve spool being controlled by said means on said main control valve spool for controlling flow of fluid from said first bore to said inlet-outlet passage.

4. A control valve for a hydraulic actuator comprising, a valve body having an inlet port adapted to be connected to a pump, first and second outlet ports adapted to be connected to a fluid reservoir, and an inlet-outlet port adapted to be connected to a hydraulic actuator, first passage means between said inlet-outlet port and said first outlet port, a check valve in said first passage means normally preventing fluid flow therethrough, first control valve means operable when actuated to open said check valve, second passage means between said inlet port and said inlet-outlet port, a three position main control valve having a first position wherein fluid is directed from said inlet port through said second passage means to said inlet-outlet port, a second position wherein fluid is directed from said inlet port to said first control valve means for actuation thereof whereby to open said check valve in said first passage means between said inletoutlet port and said first outlet port, and a third neutral position, check valve means in said second passage means preventing reverse fluid flow therethrough from said inletoutlet port, by-pass passage means between said inlet port and said second outlet port, second control valve means adapted to close said by-pass passage means when said main control valve is in its first position and to open said by-pass passage means when said main control valve is in either its second or third positions, and third control valve means having a connection to said inlet port through a fixed orifice, a connection to said second valve means, and a connection to said inlet-outlet port only when said main control valve is in its first position whereby said third control valve means serves to control said second control valve means to close said by-pass passage means when said main control valve is in its first position and to open said by-pass passage means when said main control valve is in its second and third positions.

References Cited in the file of this patent UNITED STATES PATENTS 2,575,507 Acton Nov. 20, 1951 2,654,349 Ziskal Oct. 6, 1953 2,691,964 Stickney Oct. 19, 1954 2,847,030 McRae Aug, 12, 1958 2,868,174 Shutt Jan. 13, 1959 FOREIGN PATENTS 1,128,032 France Aug. 20, 1956 

